High power short pulse laser devices are practically important in various fields. In particular, a high-peak power ultra-short pulse laser having a high peak power is practically used for processing a transparent material and medical treatment in medicine and industry.
The high-peak power ultra-short pulse laser device that has been practically used modulates a highly repeated frequency laser pulse train output from a mode-locked fiber laser oscillator into a low repeated frequency laser pulse with a light modulator, and thereafter amplifies the laser pulse train (for example, see patent document 1).
In the application of processing, attention has been focused on the cutting of a transparent material (such as glass or sapphire) by the high-peak power ultra-short pulse laser described above (for example, see patent document 2).
Recently, a method of focusing and irradiating a high-peak power ultra-short pulse laser to inside portions of a transparent member in contact with each other and causing multiphoton absorption to perform welding has been developed (for example, see patent document 3).